1. Field of the Invention
The present invention relates generally to antenna devices, electronic devices, and methods of manufacturing antenna devices and, in particular, to an antenna device having an element member and a ground member, an electronic device, and a method of manufacturing an antenna device.
2. Description of the Related Art
In recent years and continuing to the present, much attention has been paid to wireless communications technologies using UWB (Ultra-WideBand) because they can provide radar positioning information and communications with large transmission capacity. The use of UWB within a frequency band from 3.1 to 10.6 GHz has been approved by the FCC (Federal Communications Commission) of the United States since 2002.
UWB refers to a communications method for communicating pulse signals over an ultra-wideband frequency range. Therefore, antennas for use in UWB require a structure capable of sending and receiving over the ultra-wideband frequency range.
As an antenna to be used within a frequency band from 3.1 to 10.6 GHz approved by the FCC, there is proposed at least one composed of a bottom board and a power supply body (Non-Patent Document 1).
FIGS. 1A and 1B show typical antenna devices. The antenna device 10 as shown in FIG. 1A has the bottom board 11 and the inverted conical-shaped power supply body 12 disposed thereon. The cone constituting the power supply body 12 is mounted in such a manner that its outside surface forms an angle θ with respect to the axis line. With this angle θ, a desired characteristic can be obtained.
The antenna device 20 as shown in FIG. 1B has the bottom board 11 and a teardrop-shaped power supply body 22 disposed thereon, the teardrop-shaped power supply body 22 being composed of a conical body 22a and an inscribed spherical body 22b. 
Since typical ultra-wideband antenna devices have a flat-plate-shaped bottom board mounting a conical-shaped or a teardrop-shaped power supply body, they are large in size. Therefore, it is desired that they be miniaturized and made thin.
Note that there has been proposed a reverse F-shaped antenna device formed by punching a conductive tape as a thin antenna device (see, e.g., Patent Document 2).
In addition, there has been proposed a repeater antenna device having a structure in which a metallic tape wire circuit is affixed to an adhesive film to make the repeater antenna thin (see, e.g., Patent Document 3).
[Non Patent Document 1] “An Omnidirectional and Low-VSWR Antenna for the FCC-Approved UWB Frequency Band (B-1-1333)” of Proceedings of the IEICE General Conference in 2003, written by Takuya Taniguchi and Takehiko Kobayashi of Tokyo Denki University (presented at room 201 on March 22)[Patent Document 1] JP-A-2000-196327[Patent Document 2] JP-A-2003-258520[Patent Document 3] Japan Utility Model Registration No. 2503512
Since typical ultra-wideband antenna devices have a flat-plate-shaped bottom board and a conical-shaped or a teardrop-shaped power supply body disposed thereon, they are large in size and cannot easily be mounted on electronic devices or the like. Therefore, it is desired that they be miniaturized and made thin just as the loop antennas, etc., are.
The structure that is desired in this case is one that permits the ultra-wideband antenna device of Patent Document 1 to be affixed directly to a casing or the like by making it thin and flexible. In this particular case, an element member and a ground member are arranged separated from each other in the ultra-wideband antenna device. Furthermore, the frequency characteristics and directivity of the antenna vary greatly depending on the positional relationship between the element member and the ground member. If an ultra-wideband antenna device is configured to allow a conductive tape, an adhesive tape, or the like to be processed by punching in the same manner as Patent Documents 2 and 3, the element member and the ground member would come apart into pieces. Therefore, it becomes impossible to hold the positional relationship between the element member and the ground member. Consequently, this configuration cannot easily be employed.
Accordingly, the present applicant proposes the UWB flat antenna device 30 as shown in FIGS. 2A and 2B in JP-A-2006-91602. The UWB flat antenna device 30 has a dielectric base 31. On the upper surface 31a of the dielectric base 31, there are arranged an antenna element pattern 32, a strip line 33, and two ground patterns 34 and 35. Furthermore, a coaxial connector 50 is mounted at the end of the base 31. This configuration is intended to achieve the miniaturization and thinning of the device.
Meanwhile, it is considered that UWB antenna devices will be installed in mobile phones, personal computers, keyboards, mice, monitors, and the like for communication with peripheral devices. Therefore, it is desired to make the device thinner and facilitate the mounting and manufacturing of the device.